<h1> 5秒后清理Observable 可观察的对象 </h1>
<button nz-button nzType="primary" (click)="add()" [disabled]="isDisable1">
  数字++
</button>
<textarea rows="4" nz-input [(ngModel)]="initNumber"></textarea>

<button nz-button nzType="default" (click)="minus()" [disabled]="isDisable2">
  数字--
</button>

